348 power quest... head rebiuld

Well, the car has been running well but on track days i have been strugling for speed on the straights. Last year i made up some test pipes and removed the AC. It helped some.

Its time to do my major service again over this winter so i thought i would pull the heads off and freshen them up. Also i have the gear box out and am putting some lower final drive gears in to give better acceleration.

I figure the car is getting old and it may be time to freshen it up. Here are some pics as the adventure begins...
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yes, i should have done a leakdown but didn't.

Pistons? for higher compression? lightness? i have been told the motor does not have the 10.5 ratio that ferrari claims.

Yes, the engine has the black plastic timing belt covers but every timing belt service i put anti-sieze on the bolts and been lucky... maybe it helps... no problems with them yet.

once the head was off (needed a special tool to get at the head bolts) i removed the valves... there is thick crusty deposit on the outter faces of the ex valves especially....
and the inside stems were even worst. I didn't think they would be that bad.
here are some pics...
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Sounds like the plan.

yes, I tried the diff thing for 15min and couldn't get it out. I will try with it on the ground next before i start removing the shafts.

Removed the valves and did some cleaning of the head/valves and pistons. I am bring a head and the intake to a shop to get some input and maybe get it flow tested before to get a starting point and see where im at. Is there anything i have to know to make sure it is flow tested properly?
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Car history goes as follows...
Ive had it since new. It is a 1992. It has about 60000km. The first 10 or so years it had 93 Sunoco and after that Shell but not religiously... I have done the majors every 3-4yrs... so i think 5 in total i think. It has not been a problem car. Very reliable.

The first 10 years it was babied.... new car and all. But I remember one year having problems with the slow-down light coming on intermitently and going in limp mode... the dealer fixing it temporarilly but finally ended up unplugging it and worked fine. After the next service i think i just plugged everything back in and it has worked fine since.

Then i went through a few years where i hardly drove it. Then these last 4 years i started having fun with the car and going to track events and even some autoxes. I have changed the springs to 1200Ibs/600Ibs and revalved the shocks. Corner balanced, aligned, played with ride hieghts for car balance.... Put some nice rubber under it with 18X9 and 18X12 light rims in the rear. They fit and tuck in the fenders nicely with no mods to the fenders. I also removed all the susp bushings that were cracking/deforming under age and the stress of the r-compound tires and machined up some delrin... works great.

I enjoy it more then ever now and these last couple years have been tracking about 3 times a month. I have a data logger and love how much the info helps in learning to drive and tuning the car. Anyway, it has turned into a track car with the odd Sunday cruzz.

So i think it has been well looked after... I even had the injectors cleaned and flow tested 3 years ago during my last service... certanly not a neglected car.... I think with the age and mileage it would be expected to to some degree... just didn't expect that much... i am a little suprised too.


-daniel

 

droped off one of my cylinder heads at a performance head rebuilder. He happened to have a 430 head there. I took a few pics i thought some might like to see...

They are going to do some checking and come up with a plan... we were discusing going with as large an intake valve as posible. OEMs are 30.5mm intake / 27.5mm ex.

If you look at the bottom of the pic... The valve on the right is the 348 intake valve, the two valves in the middle are 430 ex valves, and 430 intake valve on the left. The port shapes between the two heads are very similar on intake and ex. The big difference is in the 430 intake ports and valves... they are much larger then in the 348 but the ex side is only a little bit larger.
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OK, we flow tested the head just to see where we are at factory...

lift in ex
.100 87 84
.200 159 140
.300 194 167
.400 212

I couldn't find any flow numbers for 348s to compair. Will flow the intake soon to see how that does.
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OK, i now have time to hopefully complete this project by spring. We flow tested the head just to see where we are at factory... then installed 1mm larger intake valves, then mounted the intake runners, then the lid. Below are the flow #s...


OEM (30.5mm)......31.5mm valve.....w/mod intake...........complete intake
...................................................runners but no lid.........with lid, no TB
lift.......in.....ex
.100.....87....84.............90
.200....159..140...........168....................166
.300....194..167...........209....................206
.400....212..................225....................223.........................211.

The OEM cam lift is .36 and i should have measured flow at that lift. Anyway with oem valves i did do a reading at .35 lift and got 208.
HP = 208 x .26 x 8 = 432.(but since it is not an all out race motor i take 75% of that and it gives me 324hp) So from my estimates i think the heads are good for 324hp in street tune if the intake system and exhaust system was not the bottle neck. These are approx. calculations and are just using them as a base for my improvements.

The 1mm larger intake valve (31.5) increased the flow and velocity. If i estimate that it would flow 220 at .35lift HP = (220x.26x8) 457hp race x 75% = 343hp street. OEM velocity was 28 and went up to 34 with the larger valve setup. Not sure what the numbers mean since i am not a flow guy and trying to understand this as i go along. Its about a 20% increase in velocity.

When i installed the intake runner the flow dropped only about 1% to apporx 340hp. So the runners seam to flow well.

The problem comes when i install the lid. It brought me back to OEM flow at .4 lift (211). The lid is very restrictive. It may have a problem with its volume but i think the throttle body opening is the big problem. I and am wondering what is the easiest way to try different size openings without hacking up the lid until i know what i have to do to it. I would like to make this lid work.